Pregnancy – Even If Incomplete – May Offer Protection Against Ovarian Cancer

Recent research found that women with a history of pregnancy – even if it was not carried to term – had a decreased risk of ovarian cancer.

Previous research has shown that pregnancy is associated with a decreased risk of ovarian cancer. Now, more updated findings reveal that the correlation may stand even if the pregnancy is not carried full-term.

“We knew that women who have previously given birth are at a decreased risk of ovarian cancer. However, we also knew that not all pregnancies result in births, hence our interest in the role of incomplete pregnancies,” study author Alice W. Lee, an assistant professor at CSU Fullerton Department of Public Health, who holds a post-doctoral degree, said in an interview with CURE®.

“Although the inverse association we found between incomplete pregnancies and ovarian cancer does not indicate a causal association, it does add to our understanding of ovarian cancer risk.”

Analyzing Ovarian Cancer Data

Lee and her team analyzed data from 15 studies that were a part of the Ovarian Cancer Association Consortium (OCAC), which is an international research collaboration. They looked at the cancer and reproductive history of more than 25,000 women – some who had ovarian cancer, some without, and women who were never pregnant, experienced incomplete pregnancies, and carried their pregnancies to term.

There was a decrease in ovarian cancer risk for women who were pregnant at some point in their life, though the association was stronger in those who had complete pregnancies. Nevertheless, a significant association was still seen in those with incomplete pregnancies.

“Incomplete pregnancies (like complete pregnancies) are associated with decreased risk of ovarian cancer.” Lee said. “Although it’s unclear why this inverse association exists, our work shows that women who have been pregnant – regardless of their pregnancy’s outcome – are afforded some protection against ovarian cancer development.”

Potential Explanations Behind the Ovarian Cancer-Pregnancy Association

At first, researchers thought that pregnancy can decrease ovarian cancer risk because monthly ovulation – which involves the rupturing and later repair of the ovary surface to release an egg – stops when a woman is pregnant.

“However, we now understand from other research that the ovary is actually not the origin of most ovarian cancers, so this explanation cannot fully account for the association,” Lee explained.

The hormonal changes that occur during pregnancy may also offer an explanation behind the association. “The hormone progesterone may be of interest since its levels are much higher during pregnancy, and it has been suggested to protect against ovarian cancer development,” Lee said.

Looking ahead, Lee said that more research is needed to better understand the potential correlation between pregnancy and ovarian cancer.

“Future research should focus on the biologic mechanisms underlying this decreased risk, as this could shed light on the causes of ovarian cancer.”

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